Error out on encoding issues while loading configuration (#4976)

news/4976.bugfix

@@ -0,0 +1 @@
+Abort if reading configuration causes encoding errors.

src/pip/_internal/baseparser.py

@@ -9,7 +9,7 @@ from distutils.util import strtobool
 
 from pip._vendor.six import string_types
 
-from pip._internal.configuration import Configuration
+from pip._internal.configuration import Configuration, ConfigurationError
 from pip._internal.utils.misc import get_terminal_size
 
 logger = logging.getLogger(__name__)
@@ -177,9 +177,6 @@ class ConfigOptionParser(CustomOptionParser):
         the environ. Does a little special handling for certain types of
         options (lists)."""
 
-        # Load the configuration
-        self.config.load()
-
         # Accumulate complex default state.
         self.values = optparse.Values(self.defaults)
         late_eval = set()
@@ -224,6 +221,12 @@ class ConfigOptionParser(CustomOptionParser):
             # Old, pre-Optik 1.5 behaviour.
             return optparse.Values(self.defaults)
 
+        # Load the configuration, or error out in case of an error
+        try:
+            self.config.load()
+        except ConfigurationError as err:
+            self.exit(2, err.args[0])
+
         defaults = self._update_defaults(self.defaults.copy())  # ours
         for option in self._get_all_options():
             default = defaults.get(option.dest)

src/pip/_internal/configuration.py

@@ -11,6 +11,7 @@ Some terminology:
   A single word describing where the configuration key-value pair came from
 """
 
+import locale
 import logging
 import os
 
@@ -283,8 +284,14 @@ class Configuration(object):
         # Doing this is useful when modifying and saving files, where we don't
         # need to construct a parser.
         if os.path.exists(fname):
-            parser.read(fname)
-
+            try:
+                parser.read(fname)
+            except UnicodeDecodeError:
+                raise ConfigurationError((
+                    "ERROR: "
+                    "Configuration file contains invalid %s characters.\n"
+                    "Please fix your configuration, located at %s\n"
+                ) % (locale.getpreferredencoding(False), fname))
         return parser
 
     def _load_environment_vars(self):